An architectural paint means the paint using for the exterior wall, interior wall, ceiling or floor of a building for functions of decoration, protection and improving living conditions. Currently, water-borne paint, which features prominently in the paint filed, contains water emulsion type paint and water solution type paint, with water as disperse medium. However, the percent of water in components of the water-borne paint is up to 35-55%, leading to consume a lot of manpower, material resource and financial resource to pack or transport the water-borne paint. Due to a short shelf life and storage life, high cost and special technology is required to overcome the bad storage stability, i.e. to avoid demixing and thickening during the storage.
The discovery of re-dispersible emulsion powder by Wacker Chemie AG, Germany, enables to dry-powdering the paint. Dry-powdered paint, generally, is a powder obtained from an emulsion by a special process, which changes the producing and storage mode, reduces producing cost, makes the pack and transport easy and safe, and prolongs the storage life and the shelf life. During application, it is mixed with solvent to form a alcohol or water based paint or quick-drying paint, with the advantages such as good adaptability, easy accessibility, and economization of some requisite chemical auxiliaries in common paint to resolve the environment pollution and to save resource. So that the dry-powdered paint has been widely used and developed. Among the products of architectural paint, high solid dry-powdered paint is invented earlier and it has a great practical value, such as powdered putty, powdered tile-like paint, powdered enamel paint, powdered water resistant paint and thermal insulation paint, etc. Thin-layer dry-powdered architectural paint is coated mostly by mixing with water and following roller coating or brush coating in-situ. According to the different requirement from the high solid dry-powdered paint, the thin-layer dry-powder architectural paint can be divided into two types: one is pure re-dispersible emulsion powder system and the other is a composition (inorganic dry-powder architectural paint) of re-dispersible emulsion powder with inorganic powdered material, such as gypsum, slaked lime and cement, etc.
In the dry-powder paint of pure re-dispersible emulsion powder system, the property mainly depends on the emulsion powder. The difference of film-forming performance between the re-dispersible emulsion powder and emulsion leads to the difference of the property between coatings, outstandingly being evident in cleaning resistance, aging resistance, etc. Therefore, this paint fails to large-scale application.
In inorganic dry-powdered paint, inorganic film-forming component, such as cement, lime or gypsum, is added, so that the cleaning resistance and aging resistance have been greatly improved and advanced. Meanwhile, the inorganic dry-powdered paint has the advantages of frost resistance and anti-mildew, as well as the good performances in the aspects of resistance to water washing, adhesion, waterproof, etc. Therefore, in European market, the inorganic dry-powdered paint has great important status. Chinese Patent CN100558834C discloses a green dry-powdered paint with containing re-dispersible emulsion powder and white cement as major constituent, wherein, it saves many additions usually used in emulsion paint and reduces the volatile organic compound. Chinese Patent CN101230214B discloses a cement-based dry-powdered paint consisted of white cement, re-dispersible emulsion powder and additions having functions of tile-like and noctilucent, with great durability. Chinese Patent CN102173710A discloses a gypsum-based dry-powdered paint comprising gypsum powder, white cement and PVA micro powder to resolve the bad durability of conventional paint through chemical bonding reaction.
However, due to the addition of the lime or cement and so on, soluble salts will be generated. The soluble salts may separate out onto the surface of coating under certain conditions. These salts are white, so that some lighter colour spots will appear on deep colour coating, which is known as the whitening phenomenon. Therefore, the inorganic dry-powder paint is only suitable for white or light colour coating.